包含几个字符操作的经典程序：数字字符转换成数值、统计单词出现次数、选择法进行字符串排序、在串中查找一个字串出现的次数、字符串的选择法排序、字符串中的大写字母改小写字母-Contains several classic characters operating procedures: digital characters into numerical, statistical word occurrences, select the sort method for strings, a strin